Heat management is an important issue within the field of illumination and, in particular, within the field of solid state based illumination, such as illumination based on light emitting diodes, LEDs. Generally, when light is emitted by a light source, heat is generated. The heat generation is commonly an undesired effect since it can affect performance and life expectance of the light sources, as well as the choice of materials and the configuration of electronics for the lighting device. Heat may also be produced in optical elements of the lighting device, such as in wavelength-converting components by Stokes shift losses.
In order to reduce the effects of the heat generation, lighting devices normally comprise a heat sink arranged to dissipate heat from the light sources and other heat generating components, typically in the direction opposite to the main (or average) light propagation direction of the lighting device. CN202040621 shows a lighting device having holes extending in the heat sink to the surroundings for increasing the heat dissipation area to the surroundings and in the shade of the lighting device.
US 2011/0298371 A1 discloses a LED light bulb with openings in a cover portion. U.S. Pat. No. 3,373,275 A discloses a one piece molded light transmitting lens cover with masked ventilation openings. US 2011/0049749 A1 discloses a replaceable illumination module with a cover cap which includes micro-weave materials with pore sizes large enough for air transfer but too small to convey water droplets. U.S. Pat. No. 3,253,675 A discloses an apparatus for absorbing acoustic energy comprising a light-transmitting member having one or more layers of a porous material which permits the transmission of light therethrough. EP 2461089 A1 discloses a lighting unit with a light transmissive lamp cap having a plurality of vent holes.
However, it would be desirable to achieve alternative solutions for improving heat dissipation from lighting devices.